With Episode 8: The Last Jedi set to hit theatres on December 15, 2017 - two years after Episode 7: The Force Awakens - it was expected that the concluding chunk of the trilogy would follow a similar pattern. However, on the movie’s IMDb page it’s listed for a US unveiling on May 24, 2019, with May 23 in Russia. Star Wars news: Episode 9 'out EARLIER than expected' - return to summer dominance?
Episode IX is indeed returning to the summer season. Star Wars: Episode IX and Next Indiana Jones Get Release Dates | StarWars.com
Keep in mind that they haven't started filming yet. Both The Force Awakens and The Last Jedi were originally announced with May release dates and then were pushed back after filming got underway. It is certainly possible the same thing will happen with Episode 9.